1. Field of the Invention
The present invention relates to a shape measuring apparatus for measuring the position of a measuring face on the basis of the light applied from a light source having a wideband spectrum to the measuring face and the interference intensity of the light applied to a reference face.
2. Description of the Related Art
Conventionally, various shape measuring apparatuses have been known in which the three-dimensional shape of an object to be measured is measured in a non-contact state using an optical system. For example, a white light interferometer is known as a shape measuring apparatus capable of three-dimensionally measuring very small objects to be measured, such as micromachines and LSIs. In this white light interferometer, the white light applied from a white light source to an object to be measured and reflected by the object to be measured is made to interfere with the white light applied from the white light source to a reference face and reflected by the reference face, a reference face position having the largest interfering light intensity is detected while the reference face is moved in the direction of the optical axis, and the height of the object to be measured in the direction of the optical axis is measured on the basis of this reference face position (refer to International publication No. 2006-068217).
As this kind of white light interferometer, a shape measuring apparatus is known as an apparatus of using simplified arithmetic processing in which the weighted average of inspection positions is calculated while the absolute value of the difference value between the interference fringe intensity values obtained before and after an optical path length difference is changed by a predetermined amount is used as a weight, and the value indicated by the weighted average is obtained as a peak position at which the absolute value of the difference value becomes the largest (refer to Japanese Patent No. 3220955).
Data actually obtained by measurement using this kind of white light interferometer is susceptible to the influence of noise, and large swells occur in some cases on the baseline of a signal depending on the characteristics of the surface of a sample.